Not only is the second syntax easier to read and not only will it work under any condition, but the first syntax might not work under all conditions:
function Object() {
// Oh crap, we have redefined Object!
return []; // return an array because we are EVIL
}
var person = new Object(); // not what we think it is
But {}
, being a syntactic construct, is immune to such evil trickery.
In addition, the object literal notation can be partially optimized at parse time, since after all there's only one object type that could be created. That may result in a minuscule performance increase.